The present invention relates to a disposable photoconductive belt assembly. More particularly, the present invention relates to a disposable cartridge having a closed-loop, flexible, photoconductive belt therein. Such a cartridge finds use in printing and copying machines.
Generally, in the process of electrophotographic or xerographic printing, a photoconductive member, such as a drum, is charged to a substantially uniform potential to sensitize its surface. In the case of a copying machine, the charged portion of the photoconductive surface is exposed to a light image of an original document being reproduced. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. In the case of a printing machine connected to a computer, the charged portion of the photoconductive surface is exposed to a light image, the shape of which is controlled by input signals from the computer. Here too, an electrostatic latent image corresponding to informational areas is recorded on the photoconductive member.
After recording the electrostatic latent image on the photoconductive member, the latent image is developed by bringing a developer material or toner into contact therewith. The developer material is attracted to the electrostatic latent image to form a powder image which is subsequently transferred to a sheet. Thereafter, the powder image is permanently affixed to the sheet in image configuration.
It is generally recognized that the cost of a printing or copying machine may be significantly reduced by implementing the concept of disposable components. Thus, it is highly desirable to be able to use relatively inexpensive components within the printing or copying machine and, after the expiration of their useful lives, to replace these components. In order to be economically competitive, these components must be easily and readily replaceable by the machine operator.
In keeping with this concept, flexible, closed-loop photoconductive belts have been used for a number of years in xerographic printing and copying machines. These photoconductive belts have several advantages over the bulky drums having photoconductive surfaces which are also used in printing and copying machines. The primary advantage of such belts is that they are relatively inexpensive and easy to replace. Thus, after a large number of uses, a drum must be either replaced or cleaned. Replacing the drum is expensive while cleaning the drum is a tedious, time-consuming chore.
To overcome these difficulties, some prior art devices employ disposable photoconductive sheets or webs mounted on the drums. However, such configurations are not popular because of difficulties in proper attachment and alignment of the sheets for correct xerographic operation. Closed-loop belts mounted on rollers are more desirable because the belts are manufactured to predetermined tolerances. In addition, the assemblies containing the belt can be fitted into the machines so as to locate the belts properly relative to the other machine components within the printing or copying machines.
Several closed-loop, photoconductive belt mechanisms are described in the prior art. U.S. Pat. No. 4,403,851 (Yanagawa) discloses a compact electrostatic copying machine having an endless photoconductive belt looped about a pair of rollers. In this copying machine, the belt assembly is attached to a cover on the top of the housing of the machine. The cover is hinged to the housing and may be opened and closed. Thus, the belt assembly moves with the cover. Also, no simple means are disclosed in this patent for detaching and replacing the photoconductive belt assembly from the cover.
U.S. Pat. No. 4,416,532 (Rosati) discloses another photoconductive belt arrangement for a copying machine. This arrangement includes many machine parts including a latch assembly and a tensioning assembly. When the tensioning assembly is deactivated, the photoconductive belt can be removed from the capstans and replaced.
U.S. Pat. No. 4,470,690 (Hoffman) discloses yet another copying machine incorporating a photoconductive belt arrangement. In this apparatus, the photoconductive belt is looped about two rollers of different sizes. The photoconductive belt assembly is disposed generally horizontally within the copier in order to take advantage of an arcuate paper injection magazine. In this patent, the belt assembly is disclosed as being removable as a self-contained unit. However, the photoconductive belt assembly includes many parts including a tensioning assembly. The tensioning assembly is used for releasing and then reapplying the tension on the belt so that it can be removed from the rollers and replaced.
It is an object of the present invention to provide a photoconductive belt assembly for a xerographic printing or copying machine which can be easily removed and replaced as a self-contained unit.
It is another object of the present invention to provide a self-contained photoconductive belt assembly which has relatively few parts and is inexpensive to manufacture.
It is a further object of the present invention to provide a self-contained photoconductive belt assembly which does not require a tensioning assembly for removing and replacing the photoconductive belt.
It is a further object of the present invention to provide a self-contained photoconductive assembly having a charging unit and a photosensor attached thereto so that they may be easily removed and replaced along with the photoconductive belt.